Fuel mixture



, Patented Aug. 31, 1943 om-rE-o STATES PATENT OFFIC FUEL MIXTURE John A. Hyson, Merwood Park, and Joseph H. Kerrick, Philadelphia, Pa., assignors to The encountered in their use.

. designated No. 4 buckwheat.

' 7 Philadelphia and Reading Coal and Iron Company, Philadelphia la, a corpora'tion of Pennsylvania No Drawing. Original application July-16,1939,

. SerialRNo. 282,968, now Patent No. 2,281,497,

. dated April 28-, 1942. Divided andthis application December 31, 1940,.Serial. No. 372,627

1 1 Claims.

able properties and characteristics.

More. specifically, the improvedfuel isamixture of arelatively large percentage, by weight,

of bituminouscoal and a relatively small percentage. of a small-sized or finely divided anthracite coal. This mixture is especially suited for use in the firing of underfeed stokers which are subject to high-peak loads and to substantial variations in load. The bituminous coalwith its relatively high volatile content provides a desirable flash which insures a rapid increasein the rate of combustion when asudden increase in load is encountered and enables. a high-peak load to e met over a desired period. The anthracite, on

the other hand, imparts; various desirable propicrties to the mixture. .efl'ect upon thefiner particlesof bituminous and henceprevents excessive loss of these fine par- It has a weighting-down ticles u the chimney under heavy-draft conditions. Thus, the efiiciency of the if-uelconsumm tion is "increased. Moreover, the anthracite, which may suitably be of. the No. 4 buckwheat variety, provides an economical source of as substantial part. of theB. t. 11. value ofthe. mixture.

Accordingly, the mixture. is ont only less expensive perton than the bituminous coal employed is encountered but they should also be such as it eontributesits proportionate share to the heat.

value. of the mixture as a whole. This mixture,

. moreover, is cheaper in relation to its B. t. 11.

value than straight bituminous. Due to the lower volatility of themixture, as compared with bituminous alone, the danger of spontaneous cmbustion ofl the fuel in the bunkers is substantially eliminated and loss from this source is thus avoided and the usual periodic .trimmingof the bunkers may be dispensed with. At the same timetthe flash of the bituminous coal, which isimportantwhen heavy peak loads are to be met, is preserved. Use of the mixture, furthermore, "is conducive to smoke abatement and to greater cleanliness in the boiler room.

Apparently the high efficiency in the used the mixture and its cleaner burning qualities are due to the previously mentioned weighting-down effect of the anthracite upon the fine particles: of

to allow as nearly a maximum boiler efflciency as possible under the burning conditions normally The water content of the composite fuel shouldbe between aboutf w and 6.4%. I

It has been found thatran exceptionally high boiler efllciency may be obtained through the use in an underfeed stoker of a mixture of substantially 80% of run or mine bituminous coal and of anthracite coal of the type generally .Such a mixture has a moisture content within the permissible range and has certain distinct advantages in addition to the high boiler eificiency already menbituminous and the coke derived therefrom. Less of these fine particles are carried away in the,

smoke or deposited in the back passes of the furnace. Thus the combustion of the bituminous is renderedmore complete by the presence of but it is consumed with higher efficiency. 30 the anthracite. This application is a d vision of our pending While the particular mixture specified is espeapplication Ser. No. 282,968; filed July 6, 1939, cially suited for underfeed stoker use under 0011- which has matured intoPatent No; 2,281,497,.isditions of heavy peak loads, such as encountered, sued April 28,. 1942. in which-a method and means for example, in the operation of a subway system, of producing the improved mixture are claimed. M it may be varied slightly for this use and other Coal mixtures of the 'typefprimarily oontemvariations may be made to adaptthe mixture for platedby the present inventionshould not only be other uses. The amount of anthracite employed, capable of relatively rapidignition and combushowever, should not be excessive since the moistion' as a sudden lncreasein' the load on a boiler 6 ture c0ntent of the armature is then likely to be increased to the point that trouble will be caused in its use. In general it may be said to be desirable toemploy between'llland 80% of bituminous and between 20 and 30% of anthracite in themixture. The two types of coal, as already explained, should be thoroughly intermixed.

This may suitably be acconiplishedbythe method higher volatility may be employed for some purposes. Its moisture content may be between 3 and 4%, its fixed carbon between and its Sulfur, per cent l.

sulphur content between 1 and 2%, its ash between and 8%, and it may have a B. t. 11. value of 14,000 or more.

i The anthracite is preferably a line buckwheat commonly designated No. 4. Its particles preferably range from %i" to $32" and it flows much like sand. It may suitably be the material which will pass through a &2" screen and will pass over a %4," screen. Not more than 5% of the material should be oversize and not more than about 25% should be undersize. There should be substantially no sub-mesh material in the anthracite. An excess of oversized particles tends to pass too much carbon to the ash while an excess of undersized particles tends to develop packing in the fuel bed with resulting uneven distribution of air and the formation of blow holes if the air pressure is increased to offset the packing. The anthracite volatile matter should range from about 4 to 8%, the moisture from about 8 to 12%, the fixed carbon from about 70 to 80%, or slightly higher, the ash from about 10 to 12%, and

the sulfur should be less than1%. Its as received B. t. u.. value is somewhat lower than the bituruinous and will ordinarily be between 11,500

and 13,000.

, Typical fuels which have been used and the mixtures formed therefrom have had the f ollowing analyses as fired:

Anthracite meteor-A ocoocnom Fixed carbon, per cent .l Volatile matter, per cent Moisture, per cent Ash, percent B. t. u. (as received) derstood that the mixture may be modified in a variety of ways without departing from the general principles and scope of the invention. The terms and expressions employed herein have been used as terms of description and not of limitation.

What we claim is:

1. An underfeed stoker fuel which comprises an intimate intermixture of between 70' and 80% by weight of bituminous coal and 20 to by weight of anthracite coal of the number 1 buckwheat size.

2. An underfeed stoker fuel which comprises an intimate intermixture of about 80% by weight of bituminous coal and about 20% by weight of anthracite coal whose particles pass through a sVscreen and over a screen.

3. An underfeed stoker fuel which comprises an intimate intermixture of between 70 and 80% by weight of bituminous coal and 20 to 30% by weight of anthracite coal of the number 4 buckwheat size, said, mixture having a moisture conanthracite coal having substantially no sub-mesh material and having a moisture content of about 8 to 12%.

5. An underfeed Stoker fuel which comprises an intermixture of between and by weight of run of the mine bituminous coal having between 16 and 22% volatile matter, and 20 to 30% by weight of a finely divided anthracite coal having substantially no sub-mesh material and having between 4 and 8% volatile matter.

6. An underfeed stoker fuel which comprises an intermixture of between '70 and 80% by weight of run of the mine bituminous coal having between 18 and 22% volatile matter and a moisture content not exceeding about 4%, and

20 to 30% by weight of a finely divided anthracite coal having substantially no sub-mesh material and having between 4 and 8% volatile matter and a moisture content of about 8 to 12%.

I. An underfeed stoker fuel whioh'comprises intermixture of between '70 and 80% by weight of run of the mine bituminous coal and 20 to 30% by weight of a finely divided anthracite coal all particles of which are capable of passing through a 5% screen and containing substantially no sub-mesh material.

8. An underfeed stoker fuel which comprises an intermixture of bituminous and anthracite coals, the anthracite constituting not more than about 30% of the mixture and being in a finely divided state but containing substantially no submesh material, the mixture having between 15 and 18% volatile matter and a moisture content an intermixture of bituminous and anthracite coals, the anthracite constituting not more than about 80% of the mixture and being in a finely divided state but containing substantially no submesh material, the mixture having between 15 and 18% volatile matter, between '70 and 77% fixed carbon, and a moisture content of between 4 and 6%.

10. An underfeed stoker fuel which comprises an intermixture of bituminous and anthracite coals, the anthracite constituting not more than about 30% of the mixture and being in a finely divided state but containing substantially no submesh material, the mixture having between 15 and 18% volatile matter, an ash content of between 7 and 9%, and a moisture content of between 4 and 6%.

11. A method of generating heat which comprises burning a mixture of anthracite and biturninous coals in a furnace, and feeding said fuel to the furnace by an underfeed Stoker, said mixture containing between '70 and 80% by weight of bituminous coal and 20 to 30% by weight of anthracite coal of the number 4.- buckwheat size.

JOHN A. HYSON.

JOSEPH H. KERR'ICKQ CERTIFICATE OF CORRECTION.

Patent No. J- L7. August 51, 19%

JOHN A HYSON, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring cor rection e e follows: Page 1 first column, line 28 for "ont" read -not-; and secontl column, line 59, for "armature" read --mixture and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 9th day of November, A. D. 19L 5 Henry Van Arsdale,

(Seal) Acting Commissioner of Patents. 

